The clock on many Windows PCs in homes and small businesses can be off by a few minutes; by default it only updates intermittently on the time.windows.com server. To digitally record TV shows, not miss meeting times, or help with other situations that involve precise timing, you should consider pointing your clock an alternate time server.

Technology blog One Tip a Day recommends the Network Time Protocol server and explains how connect to it:

Right-click your clock and choose Adjust date/time

Click on the Internet Time tab and then the Change Settings button

Replace the default time server with pool.ntp.org

Click Update Now

Do this and you should receive a confirmation that your time was successfully synchronized with the NTP server. Going forward Windows will now synchronize there once per week.